#include<stdio.h>

int main()
{
	int k, n;
	double s, a, b, c;
	s = 0.0; a = 2.0; b = 1.0;
	scanf_s("%d", &n);
	for (k = 1; k <= n; k++)
	{
		s = s + a / b;
		c = b;
		b = a;
		a = a + c;
	}
	printf("s%d=%lf\n", n, s);
	return 0;
}